I found this on https://forums.tomshardware.com and it worked for me on a Pixma mx715 BRIEFLY!
1. Turn OFF Power[br]
2. Open the print head bay (as though you were about to change inks)[br]
3. Turn ON power[br]
4. Wait for print carriage to start moving to the left and let it go past half way[br]
5. Before print carriage reaches left hand side (but after going halfway across) shut the cover.[br]
6. Leave the Printer turned on[br]
7. Good to go.[br]
[br]
(Very occasionally I have had to do this twice in a row to get past the error)
Unfortunately before I was able to do anything useful the printer ceased to start up properly. A power monitor showed a brief consumption of 6W at plug-in, then it fell to zero and the power light did not light. (So I am in iFixIt to find a solution to that. The removable power supply has been cut open…)